add u1db code (not as submodule)

1 files changed, 211 insertions, 0 deletions

diff --git a/u1db/backends/__init__.py b/u1db/backends/__init__.py
new file mode 100644
index 00000000..c8e5adc6
--- /dev/null
+++ b/u1db/backends/__init__.py
@@ -0,0 +1,211 @@
+# Copyright 2011 Canonical Ltd.
+#
+# This file is part of u1db.
+#
+# u1db is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License version 3
+# as published by the Free Software Foundation.
+#
+# u1db is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with u1db.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Abstract classes and common implementations for the backends."""
+
+import re
+try:
+    import simplejson as json
+except ImportError:
+    import json  # noqa
+import uuid
+
+import u1db
+from u1db import (
+    errors,
+)
+import u1db.sync
+from u1db.vectorclock import VectorClockRev
+
+
+check_doc_id_re = re.compile("^" + u1db.DOC_ID_CONSTRAINTS + "$", re.UNICODE)
+
+
+class CommonSyncTarget(u1db.sync.LocalSyncTarget):
+    pass
+
+
+class CommonBackend(u1db.Database):
+
+    document_size_limit = 0
+
+    def _allocate_doc_id(self):
+        """Generate a unique identifier for this document."""
+        return 'D-' + uuid.uuid4().hex  # 'D-' stands for document
+
+    def _allocate_transaction_id(self):
+        return 'T-' + uuid.uuid4().hex  # 'T-' stands for transaction
+
+    def _allocate_doc_rev(self, old_doc_rev):
+        vcr = VectorClockRev(old_doc_rev)
+        vcr.increment(self._replica_uid)
+        return vcr.as_str()
+
+    def _check_doc_id(self, doc_id):
+        if not check_doc_id_re.match(doc_id):
+            raise errors.InvalidDocId()
+
+    def _check_doc_size(self, doc):
+        if not self.document_size_limit:
+            return
+        if doc.get_size() > self.document_size_limit:
+            raise errors.DocumentTooBig
+
+    def _get_generation(self):
+        """Return the current generation.
+
+        """
+        raise NotImplementedError(self._get_generation)
+
+    def _get_generation_info(self):
+        """Return the current generation and transaction id.
+
+        """
+        raise NotImplementedError(self._get_generation_info)
+
+    def _get_doc(self, doc_id, check_for_conflicts=False):
+        """Extract the document from storage.
+
+        This can return None if the document doesn't exist.
+        """
+        raise NotImplementedError(self._get_doc)
+
+    def _has_conflicts(self, doc_id):
+        """Return True if the doc has conflicts, False otherwise."""
+        raise NotImplementedError(self._has_conflicts)
+
+    def create_doc(self, content, doc_id=None):
+        json_string = json.dumps(content)
+        if doc_id is None:
+            doc_id = self._allocate_doc_id()
+        doc = self._factory(doc_id, None, json_string)
+        self.put_doc(doc)
+        return doc
+
+    def create_doc_from_json(self, json, doc_id=None):
+        if doc_id is None:
+            doc_id = self._allocate_doc_id()
+        doc = self._factory(doc_id, None, json)
+        self.put_doc(doc)
+        return doc
+
+    def _get_transaction_log(self):
+        """This is only for the test suite, it is not part of the api."""
+        raise NotImplementedError(self._get_transaction_log)
+
+    def _put_and_update_indexes(self, doc_id, old_doc, new_rev, content):
+        raise NotImplementedError(self._put_and_update_indexes)
+
+    def get_docs(self, doc_ids, check_for_conflicts=True,
+                 include_deleted=False):
+        for doc_id in doc_ids:
+            doc = self._get_doc(
+                doc_id, check_for_conflicts=check_for_conflicts)
+            if doc.is_tombstone() and not include_deleted:
+                continue
+            yield doc
+
+    def _get_trans_id_for_gen(self, generation):
+        """Get the transaction id corresponding to a particular generation.
+
+        Raises an InvalidGeneration when the generation does not exist.
+
+        """
+        raise NotImplementedError(self._get_trans_id_for_gen)
+
+    def validate_gen_and_trans_id(self, generation, trans_id):
+        """Validate the generation and transaction id.
+
+        Raises an InvalidGeneration when the generation does not exist, and an
+        InvalidTransactionId when it does but with a different transaction id.
+
+        """
+        if generation == 0:
+            return
+        known_trans_id = self._get_trans_id_for_gen(generation)
+        if known_trans_id != trans_id:
+            raise errors.InvalidTransactionId
+
+    def _validate_source(self, other_replica_uid, other_generation,
+                         other_transaction_id):
+        """Validate the new generation and transaction id.
+
+        other_generation must be greater than what we have stored for this
+        replica, *or* it must be the same and the transaction_id must be the
+        same as well.
+        """
+        (old_generation,
+         old_transaction_id) = self._get_replica_gen_and_trans_id(
+             other_replica_uid)
+        if other_generation < old_generation:
+            raise errors.InvalidGeneration
+        if other_generation > old_generation:
+            return
+        if other_transaction_id == old_transaction_id:
+            return
+        raise errors.InvalidTransactionId
+
+    def _put_doc_if_newer(self, doc, save_conflict, replica_uid, replica_gen,
+                          replica_trans_id=''):
+        cur_doc = self._get_doc(doc.doc_id)
+        doc_vcr = VectorClockRev(doc.rev)
+        if cur_doc is None:
+            cur_vcr = VectorClockRev(None)
+        else:
+            cur_vcr = VectorClockRev(cur_doc.rev)
+        self._validate_source(replica_uid, replica_gen, replica_trans_id)
+        if doc_vcr.is_newer(cur_vcr):
+            rev = doc.rev
+            self._prune_conflicts(doc, doc_vcr)
+            if doc.rev != rev:
+                # conflicts have been autoresolved
+                state = 'superseded'
+            else:
+                state = 'inserted'
+            self._put_and_update_indexes(cur_doc, doc)
+        elif doc.rev == cur_doc.rev:
+            # magical convergence
+            state = 'converged'
+        elif cur_vcr.is_newer(doc_vcr):
+            # Don't add this to seen_ids, because we have something newer,
+            # so we should send it back, and we should not generate a
+            # conflict
+            state = 'superseded'
+        elif cur_doc.same_content_as(doc):
+            # the documents have been edited to the same thing at both ends
+            doc_vcr.maximize(cur_vcr)
+            doc_vcr.increment(self._replica_uid)
+            doc.rev = doc_vcr.as_str()
+            self._put_and_update_indexes(cur_doc, doc)
+            state = 'superseded'
+        else:
+            state = 'conflicted'
+            if save_conflict:
+                self._force_doc_sync_conflict(doc)
+        if replica_uid is not None and replica_gen is not None:
+            self._do_set_replica_gen_and_trans_id(
+                replica_uid, replica_gen, replica_trans_id)
+        return state, self._get_generation()
+
+    def _ensure_maximal_rev(self, cur_rev, extra_revs):
+        vcr = VectorClockRev(cur_rev)
+        for rev in extra_revs:
+            vcr.maximize(VectorClockRev(rev))
+        vcr.increment(self._replica_uid)
+        return vcr.as_str()
+
+    def set_document_size_limit(self, limit):
+        self.document_size_limit = limit